The multibillion-dollar effort to build Fortress America involves a combination of one of the oldest technologies in the world – the fence – and some of the newest – advanced radar, infrared cameras and drones. Despite some notable successes in deploying technology, experts warn that there have been spectacular failures: Private contractors have shoved off shoddy materials; an unforgiving environment has wreaked havoc on sophisticated systems; and ingenuitive migrants regularly scale the existing fence near San Diego.

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